Humidifiers and Dehumidifiers - Generalaire 900 water stays running

Ever since I had this humidifier installed I've had trouble with the water feeding the eveporator pad keep running after the furnace shuts off. All I have to do it disconnect to wire that feeds the soliniod valve for a second and hook it back up and it works fine for a day or so and then it happens again. Is my trouble in the valve sticking sometimes or in the power flow to it?
Any advice would help before I just start replacing parts.

How is it wired up?

What is being used to control it on and off? (sail switch, or A50 relay)

Its an A50 relay. I have it hooked to the wire for the blower that comes on when the unit calls for heat. I have a 92% Ducane furnace.

If this happens again, put the meter on it to see if you are still getting power. If you are still getting power (24 volts), then the A50 maybe sticking on you.

since I don't have a model # on your furnace, have you looked on the board to see if you have 24v HUM on it?

I looked on the board and there is a terminal marked HUM. So I'm guessing that stands for humidifier and that I can hard wire it to the board? My guy must have missed that when he went with the A50 relay set up. I'll try to figure it out tonight when I get off of work. I suppose you have to run a wire from that terminal into the controller for the humidifier. I'll look for the manual on that. Thanks!!

Before we go jumping on to this, you need to find out if it's 120volts or 24 volts.. If it's 120, then a transformer is needed.

I finally checked the voltage on the HUM terminal and it was 118V. I guess I need a transformer? Is that something you get at Home Depot? Thanks

Yes, you'll need a 24 volts transformer.. It will be in the electrical dept by the door bells.